Raspberry Pi support

Added support for hardware SPI on RPI per jscrane fork:
- Fixed a few bugs with single SPI transfers
- Aligned with optimized RF24 library fork
- Updated bmc2835 files per
http://www.airspayce.com/mikem/bcm2835/index.html
- Merged bcm files with changes from
https://github.com/farconada/RF24Network
- Added example files
- Added setup info to readme

RPi/RF24/examples/pingpair_dyn.cpp

@@ -0,0 +1,181 @@
+/*
+	TMRh20 2014 - Optimized RF24 Library Fork
+*/
+
+/**
+ * Example using Dynamic Payloads 
+ *
+ * This is an example of how to use payloads of a varying (dynamic) size. 
+ */
+
+#include <cstdlib>
+#include <iostream>
+#include <sstream>
+#include <string>
+#include "./RF24.h"
+
+
+using namespace std;
+//
+// Hardware configuration
+//
+
+// CE Pin, CSN Pin, SPI Speed
+
+// Setup for GPIO 22 CE and GPIO 25 CSN with SPI Speed @ 1Mhz
+//RF24 radio(RPI_V2_GPIO_P1_22, RPI_V2_GPIO_P1_18, BCM2835_SPI_SPEED_1MHZ);
+
+// Setup for GPIO 22 CE and CE0 CSN with SPI Speed @ 4Mhz
+//RF24 radio(RPI_V2_GPIO_P1_15, BCM2835_SPI_CS0, BCM2835_SPI_SPEED_4MHZ); 
+
+// Setup for GPIO 22 CE and CE1 CSN with SPI Speed @ 8Mhz
+RF24 radio(RPI_V2_GPIO_P1_15, RPI_V2_GPIO_P1_26, BCM2835_SPI_SPEED_8MHZ);  
+
+
+// Radio pipe addresses for the 2 nodes to communicate.
+const uint64_t pipes[2] = { 0xF0F0F0F0E1LL, 0xF0F0F0F0D2LL };
+
+bool role_ping_out = 1, role_pong_back = 0;
+bool role = 0;
+
+const int min_payload_size = 4;
+const int max_payload_size = 32;
+const int payload_size_increments_by = 1;
+int next_payload_size = min_payload_size;
+
+char receive_payload[max_payload_size+1]; // +1 to allow room for a terminating NULL char
+
+int main(int argc, char** argv){
+
+ 
+  // Print preamble:
+  printf("RF24/examples/pingpair_dyn/\n");
+
+  // Setup and configure rf radio
+  radio.begin();
+  radio.enableDynamicPayloads();
+  radio.setRetries(5,15);
+  radio.printDetails();
+
+
+/********* Role chooser ***********/
+
+  printf("\n ************ Role Setup ***********\n");
+  string input = "";
+  char myChar = {0};
+  cout << "Choose a role: Enter 0 for receiver, 1 for transmitter (CTRL+C to exit) \n>";
+  getline(cin,input);
+  
+  if(input.length() == 1) {
+	myChar = input[0];
+	if(myChar == '0'){
+		cout << "Role: Pong Back, awaiting transmission " << endl << endl;
+	}else{  cout << "Role: Ping Out, starting transmission " << endl << endl;
+		role = role_ping_out;
+	}
+  }
+/***********************************/
+
+    if ( role == role_ping_out )    {
+      radio.openWritingPipe(pipes[0]);
+      radio.openReadingPipe(1,pipes[1]);
+    } else {
+      radio.openWritingPipe(pipes[1]);
+      radio.openReadingPipe(1,pipes[0]);
+      radio.startListening();
+    }
+
+
+// forever loop
+	while (1)
+	{
+
+if (role == role_ping_out)
+  {
+    // The payload will always be the same, what will change is how much of it we send.
+    static char send_payload[] = "ABCDEFGHIJKLMNOPQRSTUVWXYZ789012";
+
+    // First, stop listening so we can talk.
+    radio.stopListening();
+
+    // Take the time, and send it.  This will block until complete
+    printf("Now sending length %i...",next_payload_size);
+    radio.write( send_payload, next_payload_size );
+
+    // Now, continue listening
+    radio.startListening();
+
+    // Wait here until we get a response, or timeout
+    unsigned long started_waiting_at = millis();
+    bool timeout = false;
+    while ( ! radio.available() && ! timeout )
+      if (millis() - started_waiting_at > 500 )
+        timeout = true;
+
+    // Describe the results
+    if ( timeout )
+    {
+      printf("Failed, response timed out.\n\r");
+    }
+    else
+    {
+      // Grab the response, compare, and send to debugging spew
+      uint8_t len = radio.getDynamicPayloadSize();
+      radio.read( receive_payload, len );
+
+      // Put a zero at the end for easy printing
+      receive_payload[len] = 0;
+
+      // Spew it
+      printf("Got response size=%i value=%s\n\r",len,receive_payload);
+    }
+    
+    // Update size for next time.
+    next_payload_size += payload_size_increments_by;
+    if ( next_payload_size > max_payload_size )
+      next_payload_size = min_payload_size;
+
+    // Try again 1s later
+    delay(100);
+  }
+
+  //
+  // Pong back role.  Receive each packet, dump it out, and send it back
+  //
+
+  if ( role == role_pong_back )
+  {
+    // if there is data ready
+    if ( radio.available() )
+    {
+      // Dump the payloads until we've gotten everything
+      uint8_t len;
+
+      while (radio.available())
+      {
+        // Fetch the payload, and see if this was the last one.
+	len = radio.getDynamicPayloadSize();
+	radio.read( receive_payload, len );
+
+	// Put a zero at the end for easy printing
+	receive_payload[len] = 0;
+
+	// Spew it
+	printf("Got payload size=%i value=%s\n\r",len,receive_payload);
+      }
+
+      // First, stop listening so we can talk
+      radio.stopListening();
+
+      // Send the final one back.
+      radio.write( receive_payload, len );
+      printf("Sent response.\n\r");
+
+      // Now, resume listening so we catch the next packets.
+      radio.startListening();
+    }
+  }
+}
+}
+
+